In gas turbine engines, air is compressed at an initial stage, is subsequently heated in combustion chambers, and the hot gas so produced passes to a turbine that, driven by the hot gas, does work which may include rotating the air compressor.
In a typical industrial gas turbine engine, a number of combustion chambers combust fuel. Hot gas flowing from these combustion chambers is passed via respective transitions (also referred to as ducts or transition pieces) to respective inlets of the turbine. More specifically, a plurality of combustion chambers are commonly arranged radially about a longitudinal axis of the gas turbine engine, and likewise radially arranged transitions respectively include outlet ends that converge to form an annular inflow of hot gas to the turbine inlet. Each transition outlet is joined by a seal to a vane rail of a row 1 vane segment at the turbine inlet. Adjacent component growth variances due to thermal expansion, thermal stresses, and vibrational forces from combustion dynamics all affect design criteria and performance of such a seal. Consequently, the design of such a seal has presented a challenge that resulted in various approaches that attempt to find a suitable balance between seal cost, reliability, durability, installation and repair ease, performance, and affect on adjacent components.
FIG. 1 provides a schematic cross-sectional depiction of a prior art gas turbine engine 100. The gas turbine engine 100 includes a compressor 102, a combustion chamber 108 (such as a can-annular combustion chamber), and a turbine 110. During operation, in axial flow series, the compressor 102 takes in air and provides compressed air to a diffuser 104, which passes the compressed air to a plenum 106 through which the compressed air passes to the combustion chamber 108, which mixes the compressed air with fuel (not shown), providing combusted gases via a transition 114 to the turbine 110, which may generate electricity. A shaft 112 is shown connecting the turbine 110 to drive the compressor 102. Air from the compressor 102 also travels to the turbine 110 by various channels (not shown in FIG. 1) to provide higher pressure air that surrounds and may enter the hot gas path as it passes through the turbine 110. A gap between the transition 114 and the turbine 110 is indicated by 115, and is the subject of further discussion herein.
FIG. 2 provides a cross-sectional view of the gap 115 between a transition exit frame 116 and a vane rail 132 of a row 1 vane segment 130 of a turbine inlet. FIG. 2 depicts prior art inner and outer seals 120, 122 along a respective inner and outer diameter section of the exit frame 116, to join the exit frame 116 to the vane rail 132 of a row 1 vane segment 130. The row 1 vane segment 130 includes a single airfoil 134 and is supported along an inner wall 136 by an inner vane attachment structure 140 and at a downstream outer end by an outer vane attachment structure 142 that connects to a row 1 turbine blade ring 144. The vane rail 132 of the row 1 vane segment 130 includes a respective lip 138, 139 that engages a slot 121, 123 in the respective inner and outer seals 120, 122. Each slot 121, 123 provides for axial movement and limited radial movement.
Various designs of the conventional seal 120, 122 have been developed, such as a heavy seal design, which has an inherently large mass/inertia, and may cause wear to the exit rail 116 and adjacent components, when the heavy seal is excited by dynamic forces during engine operation between the exit rail 116 and the vane rail 132. Similarly, a conventional thin seal design has been developed, with an inherently small mass/inertia, which despite reducing the likelihood of excessive wear to adjacent components, may wear at an excessive rate, due to direct abrasive contact with an inherently hard superalloy material used to form the vane rail 132 of the row 1 vane segment 130.
Thus, it would be advantageous to provide a seal for the gap between the transition exit frame and the vane rail, which avoids the shortcomings of the conventional designs of the heavy seal and the thin seal.